[v3] Implement std::is_aggregate.

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 6707caa..a5e7048 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -3062,6 +3062,25 @@  template <typename _From, typename _To>
 #endif
 #undef _GLIBCXX_NO_BUILTIN_HAS_UNIQ_OBJ_REP
 
+#ifdef __has_builtin
+# if !__has_builtin(__is_aggregate)
+// Try not to break non-GNU compilers that don't support the built-in:
+#  define _GLIBCXX_NO_BUILTIN_IS_AGGREGATE 1
+# endif
+#endif
+
+#ifndef _GLIBCXX_NO_BUILTIN_IS_AGGREGATE
+#define __cpp_lib_is_aggregate 201703
+  /// is_aggregate
+  template<typename _Tp>
+    struct is_aggregate
+    : bool_constant<__is_aggregate(remove_cv_t<_Tp>)> { };
+  /// is_aggregate_v
+  template<typename _Tp>
+    inline constexpr bool is_aggregate_v = is_aggregate<_Tp>::value;
+#endif
+#undef _GLIBCXX_NO_BUILTIN_IS_AGGREGATE
+  
 #endif // C++17
 
 _GLIBCXX_END_NAMESPACE_VERSION
diff --git a/libstdc++-v3/testsuite/20_util/is_aggregate/requirements/explicit_instantiation.cc b/libstdc++-v3/testsuite/20_util/is_aggregate/requirements/explicit_instantiation.cc
new file mode 100644
index 0000000..4c189cd
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/is_aggregate/requirements/explicit_instantiation.cc
@@ -0,0 +1,29 @@ 
+// { dg-options "-std=gnu++1z" }
+// { dg-do compile { target c++1z } }
+
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// NB: This file is for testing type_traits with NO OTHER INCLUDES.
+
+#include <type_traits>
+
+namespace std
+{
+  typedef short test_type;
+  template struct is_aggregate<test_type>;
+}
diff --git a/libstdc++-v3/testsuite/20_util/is_aggregate/requirements/typedefs.cc b/libstdc++-v3/testsuite/20_util/is_aggregate/requirements/typedefs.cc
new file mode 100644
index 0000000..4b0358c
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/is_aggregate/requirements/typedefs.cc
@@ -0,0 +1,32 @@ 
+// { dg-options "-std=gnu++1z" }
+// { dg-do compile { target c++1z } }
+
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// NB: This file is for testing type_traits with NO OTHER INCLUDES.
+
+#include <type_traits>
+
+void test01()
+{
+  // Check for required typedefs
+  typedef std::is_aggregate<int>	test_type;
+  static_assert( std::is_same<test_type::value_type, bool>::value );
+  typedef std::integral_constant<bool, test_type{}()> bool_type;
+  static_assert( std::is_same<test_type::type, bool_type>::value );
+}
diff --git a/libstdc++-v3/testsuite/20_util/is_aggregate/value.cc b/libstdc++-v3/testsuite/20_util/is_aggregate/value.cc
new file mode 100644
index 0000000..6168d9c
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/is_aggregate/value.cc
@@ -0,0 +1,96 @@ 
+// { dg-options "-std=gnu++1z" }
+// { dg-do compile { target c++1z } }
+
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <type_traits>
+#include <testsuite_tr1.h>
+#include <tuple>
+
+template <class... T> void pos()
+{
+  static_assert((std::is_aggregate_v<T> &&...));
+}
+
+template <class... T> void neg()
+{
+  static_assert((!std::is_aggregate_v<T> &&...));
+}
+
+void test01()
+{
+  using namespace __gnu_test;
+  using __gnu_test::test_category;
+  using std::is_aggregate;
+
+  // Positive tests.
+  static_assert(test_category<is_aggregate,
+		ClassType>(true), "");
+  static_assert(test_category<is_aggregate,
+		UnionType>(true), "");
+  static_assert(test_category<is_aggregate,
+		SLType>(true), "");
+  static_assert(test_category<is_aggregate,
+		NoexceptMoveAssignClass>(true), "");
+  static_assert(test_category<is_aggregate,
+		unsigned[3]>(true), "");
+  static_assert(test_category<is_aggregate,
+		unsigned[3][2]>(true), "");
+  static_assert(test_category<is_aggregate,
+		unsigned[]>(true), "");
+  static_assert(test_category<is_aggregate,
+		unsigned[][2]>(true), "");
+  static_assert(test_category<is_aggregate,
+		EnumType[3]>(true), "");
+  static_assert(test_category<is_aggregate,
+		EnumType[3][2]>(true), "");
+  static_assert(test_category<is_aggregate,
+		EnumType[]>(true), "");
+  static_assert(test_category<is_aggregate,
+		EnumType[][2]>(true), "");
+  pos<ClassType, UnionType, SLType, NoexceptMoveAssignClass,
+      unsigned[3], unsigned[3][2], unsigned[], unsigned[][3]>();
+
+  // Negative tests.
+  static_assert(test_category<is_aggregate,
+		AbstractClass>(false), "");
+  static_assert(test_category<is_aggregate,
+		PolymorphicClass>(false), "");
+  static_assert(test_category<is_aggregate,
+		ExplicitClass>(false), "");
+  static_assert(test_category<is_aggregate,
+		char>(false), "");
+  static_assert(test_category<is_aggregate,
+		unsigned char>(false), "");
+  static_assert(test_category<is_aggregate,
+		signed char>(false), "");
+  static_assert(test_category<is_aggregate,
+		unsigned>(false), "");
+  static_assert(test_category<is_aggregate,
+                bool>(false), "");
+  static_assert(test_category<is_aggregate,
+                float>(false), "");
+  static_assert(test_category<is_aggregate,
+                double>(false), "");
+  static_assert(test_category<is_aggregate,
+		EnumType>(false), "");
+  static_assert(test_category<is_aggregate,
+		void>(false), "");
+  neg<AbstractClass, PolymorphicClass, ExplicitClass, char, unsigned,
+      bool, float, double, void>();
+}